Vehicles in general, and at least to some extent heavy vehicles in particular, are in focus of ongoing research and development relating to, inter alia, fuel efficiency and reduction of exhaust emissions. Factors such as growing official concern about pollution and air quality, e.g. in urban areas, have led to the adoption of emission standards and rules in many jurisdictions.
In the operation of heavy vehicles such as trucks, buses and the like, over time, vehicle economy has also had an ever increasing impact on the profitability of the business in which they are used. Apart from the procurement cost of a vehicle, the main expense items for routine operation are pay for the driver, repair and maintenance costs and fuel for propulsion. It is therefore important to try as far as possible to reduce costs in each of these areas.
One area in which development is at least partly stimulated by an endeavour to reduce emissions and fuel costs is that of hybrid vehicles. Hybrid vehicles use two or more power sources, and one usual type of such vehicles is the electric hybrid vehicle, in which, e.g. in addition to an internal combustion engine, one or more electrical machines may be used to generate torque/force to act upon the tractive wheels of the vehicle.
Electrical machines afford the advantage of making it possible for electrical energy to be converted to propulsive force with a relatively high degree of efficiency by the electrical machine, which at the same time may also be used to apply a braking force to the vehicle's tractive wheels and use the absorbed kinetic energy to regenerate electrical energy for feeding back to the electrical system of the vehicle and in particular to an energy storage. The regenerated energy may subsequently be reused by the electrical machine to generate propulsive force. Hybrid vehicles thus provide a way of reducing fuel consumption.
However, irrespective of the particular kind of vehicle being used, it is also important that the vehicle is operated in an economical way by their drivers, since the manner a vehicle is operated also may have a large impact on overall fuel economy. This has led to the development of systems intended, for example, to make it easier for drivers and owners to assess whether vehicles are actually being operated in a fuel economizing way.